Mini CAD Design Help

Question

Hello,

I would first like to say that I am not a professional programmer.  My degree is in electronic engineering and I work at a steel fabrication shop.  My function at the shop is designing automated tooling.  Because of my love for C++ and C# I frequently get programming projects thrown my way.  The apps I mostly develop are utilities that we use in the office.

Because I don't work on a team of developers and that I am not a computer science major I feel like my development efforts lack the proper design needed up front to yield strong software.  Having said that is why I am asking for your help.


I need to develop a simple CAD type app that will allow the user to create and edit a simple 2d parts to be produced on a CNC machine.  I know you are thinking why don't you use AutoCAD or any other package that all ready exist?  The answer is I have thought of doing a VBA app for AutoCAD, but I feel that this should be simple enough, why tie up an AutoCAD license when we just need to draw a few circles and rectangles.


What I was thinking of is creating some type of a custom class that would define the entities:

For example:   Circle Class, Rectangle Class, Line Class,  ETC.   these classes will contain x,y values for the end points as well as methods on how to draw each entity on the screen.


How do you select a entities from the screen so that they may be edited..etc?

What about a dimension that could reference two other entities?


I may be way off base on this thing, if that is the case pleas let me know as well as any better approaches!  Please guide me through this design, I am ready to learn!!!


Mike